Motor with light beam sensor

I need a small electric moror to be triggered when a light beam is interupted, then turn off when the beam is restored.
Any ideas on how I might go about doing this?
I am a novice with electronics, so parts and diagrams would be good.
Thank you!
Jeff

Not enough info--

Is the motor AC or DC? How big is "small"?

How far between the light beam source and the sensor?

Can the light beam be IR or do you want it to be visible?

What are the ambient light conditions?